[BFW-5545] [BUG] MK4 keeps requesting filament path to be cleared upon empty spool change

[bolsoncerrado]

Please, before you create a new bug report, please make sure you searched in open and closed issues and couldn't find anything that matches.

Printer type -

MK4

Printer firmware version - [e.g. 4.0.5, ...]

Any

Original or Custom firmware - [Original/Custom]

Original

Optional upgrades - [e.g. Filament Runout Sensor]

Stock Factory Assembled MK4

USB drive or USB/Octoprint

USB

Describe the bug

1. Start a print
2. Spool runs out of filament
3. Filament sensor kicks in
4. Filament is removed BUT
5. even if you reply YES to the "was filament removed ok?" the printer KEEPS asking you to remove filament. Nothing helps, the dial, the clicky, nothing. Only a RESET, ruining the print.
6. Upon rebooting filament sensor works as intended, so there's no debris no filament messing the sensor, no nothing.

How to reproduce

Read above.

Expected behavior

Since it has happened to me already TWICE and non correlative, I asume this is a firmware glitch. I already opened the idler door and removed any filament (first time none was there, second time a section was there, I chose NO to the question, but apparently it didnt detect I removed it), blowed air, moved filament on the port hole, nothing helps when the bug is present. ONLY Reset button fix the issue and once the printer reboots, everything works as intended.

G-code

No particular gcode.

Video

Next time it happens I'll tape it.

[marcelismus]

+1

But after the last time the restart didn't help, sensor calibration also shows always "NO". I need to push the filament to the left, but after that the calibration failed. After a little test print I retried with success. ¯_(ツ)_/¯ I'm wondering if it's a firmware bug or a hardware problem or both...

[bolsoncerrado]

@marcelismus what fw version did u have issues with? mine is 4.6.1 -- i'll install alpha3 now.

[unclej84]

I am having the same issue with 4.7.1 firmware - goes to park position, unloads and shows confirm screen (selected "yes") but still shows to clear the path

[unclej84]

Made a test with colorchange today and there the filament change worked - don't know what the difference between both cases (color change <-> filament runout) internally is

[bolsoncerrado]

Idk either but I lost another print today again, pretty frustrating.

[unclej84]

@bolsoncerrado are you on alpha3 now or still on 4.6.1?

[bolsoncerrado]

Now on 4.7

[arcenik86]

Confirmed issue on 4.7.1, however I did get it to clear after inserting and removing filament quickly a few times. Before doing so, verified there was no filament in the idler area. New MK4 build, third print.

[bolsoncerrado]

I tried that technique and it didnt work for me :(

[IftiBashir]

I would consider this a rather serious issue. Have Prusa responded?

[bolsoncerrado]

No :(

[zhiyao]

It happened to me as well twice.

I realized the filament sensor is not calibrated for me and will always register as a detected filament.

Temp Fix: The only way to fix this is to do a control > filament sensor calibration.

Proposed Fix: There should have been a way to overwrite the sensor during such an issue.

[unclej84]

Firmware 4.7.2 got released. Has anyone already tested, if it is fixed? Release note does not mention anything related.

[bolsoncerrado]

Why would they? No one from Prusa ever commented here :(

[MilleniumDawn]

Same issue on v5.0.0-alpha4. Stuck on requesting filament path to be cleared.

[derthomers]

same here on 5.0.0-alpha4. pushing in and pulling out a piece of filament multiple times worked in some cases. had it 8 times in 2 weeks. also on 5.0.0-alpha1..3. that really tends to ruin your print if you want to empty a spool completely before switching to a new one.

[bolsoncerrado]

Happens also if you plan to leave and don't trust enough on the filament sensor stopping the print while away if spool dries out, hence if you manually opt to change filament manually, sensor may ruin the print awaiting you remove the filament you've already acknowledged to have removed correctly.

Pretty absurd altogheter.

[arcenik86]

Just wanted to comment that this is easily duplicated with a filament change from the printer menu as well. Even after you confirm the filament is removed (yes on the prompt), you have to toggle the filament in and out for the printer to recognize nothing is loaded.

[bolsoncerrado]

What I just said yep.

[micro17]

Had the same odd behaviour today. Would be nice if Prusa can response if this is a software or hardware bug.

For me it cleared after putting the filament in and out multiple times

[bolsoncerrado]

SOunds to me they have a severe hardware design issue with this filament sensor placement :(

This radio silence is nothing but worrysome!

I also wonder if XL people is having the same issue...

EDIT: Apparently, they're:

https://www.facebook.com/groups/Prusai3users/posts/2417025891815211/

[marcelismus]

I think the problem is that the sensor is blocked by fine strings of unloaded filament. It often works if you put filament in and out many times or print a little longer. Whether design flaw (and as far as I know, the sensor cannot be reached "just like that") or just too sensitive, no idea. But a "No filament loaded" button is necessary.

[bolsoncerrado]

Well it's quite absurd the screen asks you "was the filament removed correctly?" just to ask you again to please remove the filament from the sensor path when you can't clearly reach it AND no other option (specially mid print) left than pray that wiggling multiple times the new filament will trigger the sensor :(

So I think it's both a hardware design flaw (like having a hole that gravity will end up filling with dust and such anyway) and a firmware issue...

[FliesWithWind]

+1 on this. It just happened to me when I runed out of filament. Wasted 24h of print....

[HaWiWe]

I had this happen a few times and could fix it by sticking the filament in and pulling out again a few times. It seems the hall sensor does not spring back, you can notice that there is no resistance when doing the above. At least that's what I think is happening.

[unclej84]

In the Podcast they just mentioned that new final firmware with input shaping will be released (around) Friday - let's see if this included

[Shushuda]

I just had this issue on 5.0.0-RC. The ball didn't spring back, there was no resistance. Inserting and pulling out a looot of times very rapidly finally made it spring back, resistance was there and the printer started detecting filament correctly.

[bolsoncerrado]

I think all these posts prove they have a serious hw design issue...

[Nulifier]

Something that worked for me to prevent the print from failing is to bypass the filament sensor when it gets into this stuck state.

What I did after receiving the remove the filament from the filament sensor message:

1. Remove the LoveBoard-cover-right using the M3 screw on the right side of the extruder. (Link)
2. Unplug the filament sensor cable from the lower connector. I found a pair of tweezers helpful. (Link)
3. The message should clear and you should be left with the normal load filament message
4. Install the filament sensor cable again
5. Reinstall the LoveBoard-cover-right (Its important to do it now as once you load the filament the extruder will start zipping around)
6. Load the filament

Obviously this involves some delicate work in the middle of a print and take your own precautions but it did allow me to resume a 6 hour print after hour 4. But definitely needs to be fixed on a hardware or software level.

[bolsoncerrado]

Perhaps a cleaner, less risky way would be to add some small reset button somewhere to cut the power just enough for the message to clear....